I would say, locks must automatically get locked if vehicle is driven and speed is over 5 mph and unlocked if engine is off. This is important safety feature.

Also, normally if you press unlock button short it will unlock only front door depending where it was pressed, you pressed it a lil bit longer it will unlock all doors. If you pressed button at the back door only that door would be unlocked.

If Lexus doesn't provide it, I know some Toyotas don't have it, it is bad.However you can add any aftermarket alarm system which will handle such cases. Also, you do NOT leave your belongs un-attended, otherwise "it would be removed by security personnel" which was the case. Man, keep your eyes on your stuff.....this is the only advice I can give, especially is you live in crime-zone....